000 AXPZ20 KNHC 112155 TWDEP TROPICAL WEATHER DISCUSSION NWS NATIONAL HURRICANE CENTER MIAMI FL 2205 UTC TUE DEC 11 2012 TROPICAL WEATHER DISCUSSION FOR THE EASTERN PACIFIC OCEAN FROM THE EQUATOR TO 32N...EAST OF 140W. THE FOLLOWING INFORMATION IS BASED ON SATELLITE IMAGERY...WEATHER OBSERVATIONS...RADAR...AND METEOROLOGICAL ANALYSIS. BASED ON 1800 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH 2145 UTC. ...INTERTROPICAL CONVERGENCE ZONE/MONSOON TROUGH... THE MONSOON TROUGH EXTENDS W FROM THE COAST OF COLOMBIA AT 08N78W ACROSS THE EXTREME SOUTHERN COAST OF PANAMA TO 08N92W...THEN TURNS NW TERMINATING AT AN EMBEDDED LOW PRESSURE CENTER AT 10.5N103W. LOW LEVEL WINDS INDICATE THAT THE ITCZ FORMS W OF THE LOW PRESSURE CENTER AND CONTINUES W TO 11N115W...THEN DIPS SW TO BEYOND 08N140W. SCATTERED MODERATE ISOLATED STRONG CONVECTION IS OBSERVED FROM 04.5-09N E OF 86W...WITHIN 60 NM EITHER SIDE OF A LINE FROM 11N114W TO 13N125W...AND WITHIN 90 NM EITHER SIDE OF A LINE FROM 13N123W TO 08N124W TO 09N130W. THE EMBEDDED SURFACE LOW IS ACCOMPANIED BY SCATTERED MODERATE ISOLATED STRONG CONVECTION WITHIN 45 NM EITHER SIDE OF A LINE FROM 09.5N99W TO 09N103W. SCATTERED MODERATE CONVECTION IS ALSO OBSERVED WELL N OF THE EXPOSED LOW LEVEL CENTER...WITHIN 45 NM OF 13N101W. THIS LOW IS EXPECTED TO MOVE W-NW TONIGHT INTO AN AREA OF INCREASING W SHEAR AND SHOULD WEAKEN TO AN OPEN TROUGH ON WED. SINCE THIS LOW PRES IS LIKELY TO GENERATE ONLY NE-E-SE WINDS AT 15-20 KT OVER ITS NORTHERN PERIPHERY WITH SEAS 5-7 FT...IT IS NOT MENTIONED IN THE TEXT HIGH SEAS...BUT WAS DEPICTED ON THE 24 HOUR PROGNOSTIC MARINE FACSIMILE CHARTS. ...DISCUSSION... ALOFT...AN UPPER LEVEL LONGWAVE TROUGH DISSECTS N AMERICA WITH ITS MEAN AXIS CONTINUING SW INTO THE DISCUSSION AREA ALONG 32N102W TO 21N114W. A REINFORCING SHORTWAVE TROUGH IS APPROACHING THE W PORTION AND IS CURRENTLY ALONG 36N130W TO 35N144W. AN UPPER CYCLONE HAS CUT OFF AT 25N138W. A SHORTWAVE RIDGE EXTENDS FROM 32N140W TO TO A CREST AT 30N118W. SOME UPPER MOISTURE IS NOTED OVER SOUTHERN CALIFORNIA AND NEW MEXICO AND IS SHIFTING SE TOWARDS NORTHERN OLD MEXICO. THE REINFORCING SECONDARY TROUGH IS PRECEDED BY A DENSE...BUT VERY NARROW MOISTURE BAND. OTHERWISE THE UPPER LEVELS APPEAR VERY DRY FROM 21-32N W OF 105W. THE UPPER FLOW IS ZONAL ACROSS THE TROPICS FROM 10-21N TO THE W OF 95W...AND IS ADVECTING DENSE UPPER MOISTURE EASTWARD TO 105W WHERE THE MOISTURE PLUME TURNS NE IN RESPONSE TO THE LONGWAVE TROUGH OVER THE CONUS. THIS MOISTURE FEEDS INTO THE CONVECTION ALONG A COLD FRONT EXTENDING SW FROM GEORGIA TO THE MEXICAN COAST AT 19N. AN UPPER ANTICYCLONE IS OVER S AMERICA AT 07N72W WITH A RIDGE EXTENDING NW TO 10N88W. THE ASSOCIATED UPPER DIFFLUENCE IS ENHANCING CONVECTION ALONG THE MONSOON TROUGH AS PREVIOUSLY DESCRIBED...WITH THE RESULTANT DEBRIS MOISTURE ADVECTED NE ACROSS PANAMA AND COSTA RICA. ELSEWHERE AT THE LOW LEVELS...NW WINDS CONTINUE AT 15-20 KT ACROSS THE GULF OF CALIFORNIA WATERS N OF 25N...BUT ARE EXPECTED TO DIMINISH TO 10-15 KT LATE TONIGHT. A SURFACE RIDGE EXTENDS FROM 32N140W TO 18N108W. NE WINDS AT 15-20 KT ARE CROSSING THE RIDGE OVER THE AREA N OF 10N TO THE W OF 130W WITH SEAS TO 9 FT IN THE ACCOMPANYING NE SWELL. THE GRADIENT IS EXPECTED TO TIGHTEN ON WED WITH THE NE WINDS INCREASING TO 20-25 KT TO THE W OF A LINE FROM 30N128W TO 24N140W. THE RIDGE WILL WEAKEN LATE WED ALLOWING A COLD FRONT TO MOVE SE INTO THE N-CENTRAL WATERS FROM 32N118W TO 24N124W ON WED NIGHT...REACHING FROM 30N118W TO 24N120W ON THU...AND PASSING ACROSS THE BAJA PENINSULA AND THE GULF OF CALIFORNIA ON FRI. NE WINDS WILL CONTINUE AT 20-25 KT WITH SEAS 7-10 FT FROM 12-20N W OF 132W. THESE NW 15-20 KT WINDS WILL ARRIVE AT THE W COAST OF THE BAJA PENINSULA THU NIGHT BUT DIMINISH TO 15 KT BEFORE REACHING SOUTHERN BAJA ON FRI NIGHT. GENERALLY EXPECT SEAS OF 3-5 FT ALONG WESTERN BAJA THROUGH THU THEN BUILDING 5-8 FT IN THE NW SWELL ON THU NIGHT AND FRI. LIGHT AND VARIABLE WINDS ARE EXPECTED ACROSS THE GULF OF CALIFORNIA ON WED...BECOMING SOUTHERLY WED NIGHT AND INCREASING 15-25 KT ON THU AHEAD OF THE COLD FRONT. THE POST FRONTAL FLOW IS NOT EXPECTED TO BE VERY STRONG ACROSS THE GULF OF CALIFORNIA. GAP WINDS... GULF OF TEHUANTEPEC...A COLD FRONT IS CURRENTLY ADVANCING S ACROSS THE GULF OF MEXICO WITH THE ASSOCIATED NORTHERLY WINDS EXPECTED TO SURGE AT 15-20 KT THROUGH THE CHIVELA PASS LATE TONIGHT...GRADUALLY INCREASING ON WED REACHING GALE FORCE AROUND SUNSET WED...FURTHER INCREASING TO 40 KT LATE WED NIGHT. THE GALE SHOULD PERSIST THROUGH SUNRISE THU THEN RAPIDLY DIMINISH THU NIGHT AND FRI. GULF OF PAPAGAYO...NE WINDS WILL CONTINUE TO PULSE AT 10-15 KT WITH AN OCCASIONAL SURGES TO 15-20 KT TONIGHT INTO EARLY WED. THESE NE WINDS ARE EXPECTED TO INCREASE TO 20-25 KT BEGINNING LATE WED AND CONTINUING THROUGH EARLY FRI. $$ NELSON